EGFR and lung adenocarcinoma: The exon 19 in-frame deletion is another important genetic variant for the clinical course of lung adenocarcinoma in which the EGFR exon 19 in-frame deletion produced a better response to gefitinib and erlotinib in patients with lung adenocarcinoma [23], and another study illustrated that the overall survival in advanced lung adenocarcinoma patients with EGFR exon 19 in-frame deletions was better than those with EGFR L858R expression [24].